The invention discloses a light distribution method of a vehicle brake lamp. The light distribution method of the vehicle brake lamp is characterized by comprising an LED light source and an inner light distribution mirror; a discrete material is arranged in a substrate of the inner light distribution mirror; and emitted light of the LED light source is emitted out after passing through the inner light distribution mirror. The light distribution method is adopted; and the novel discrete material is used as an auxiliary material of the inner light distribution mirror, so that output light rays are scattered more uniformly, bright and dark areas formed on the surface of the inner light distribution mirror after lightening can be effectively weakened and eliminated, the illumination is uniform and beautiful, and the internal structure and light source selection is wider and more various.